Chapter 18 Urinary System and Fluid Balance PDF

COLLEGE OF MEDICAL TECHNOLOGY Evolve. Calayan Educational Foundation, Inc. Adapt. Overcome. CEFI is now ready....

COLLEGE OF MEDICAL TECHNOLOGY Evolve. Calayan Educational Foundation, Inc. Adapt. Overcome. CEFI is now ready. Case Study 57-year-old Mark is living proof that a person can live with type 2 diabetes. Since being diagnosed with the condition 15 years ago, he has Chapter 18 taken good care of himself, watching his diet and regularly monitoring his blood glucose and blood pressure at home. Urinary System and Therefore, he was immediately aware when his blood pressure began Fluid Balance to rise. He also felt tired much of the time, and his face appeared puffy. ANA101: His physician confirmed the hypertension and detected generalized ANATOMY & PHYSIOLOGY edema. After ordering several laboratory tests, he concluded that Mark WITH PATHOPHYSIOLOGY was suffering from chronic renal failure. Explain the cause of chronic renal failure and predict the results of MARK MAGBUHOS, RMT Mark’s blood test and urinalysis that led to this diagnosis. College of Medical Technology What is the probable prognosis for Mark in the future? COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Urinary System Urinary System The urinary system is the major excretory system of the body. Some organs in other systems also eliminate wastes, but they are not able to compensate in the case of kidney failure.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Urinary System Functions Components of the Urinary System 1. Excretion Two kidneys 2. Regulation of blood volume and blood pressure Two ureters 3. Regulation of blood solute concentration One urinary bladder 4. Regulation of extracellular fluid pH One urethra 5. Regulation of red blood cell synthesis 6. Regulation of Vitamin D synthesis Urinary System COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Kidney Characteristics Kidney Structures Bilateral retroperitoneal organs Renal capsule: Shape and size: connective tissue around each kidney bean shaped protects and acts as a barrier weighs 5 ounces (bar of soap or size of fist) Hilum: Location: indentation between 12th thoracic and 3rd lumbar vertebra contains renal artery, veins, nerves, ureter COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Kidney Structures Kidney Structures Renal sinus: Renal pyramid: contains renal pelvis, blood vessels, fat junction between cortex and medulla Renal cortex: Calyx: outer portion tip of pyramids Renal medulla: Renal pelvis: inner portion where calyces join narrows to form ureter  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Nephron The nephron is the functional unit of the kidney. Each kidney has over one million nephrons. There are two types of nephrons in the kidney: juxtamedullary cortical Approximately 15% are juxtamedullary The nephron includes the renal corpuscle, proximal tubule, loop of Henle, distal tubule and collecting duct COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Renal Corpuscle and Filtration Membrane Nephron Components Renal corpuscle: structure that contains a Bowman’s capsule and glomerulus Bowman’s capsule: enlarged end of nephron opens into proximal tubule contains podocytes (specialized cells around glomerular capillaries) Glomerulus: contains capillaries wrapped around it  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Nephron Components Filtration membrane: in renal corpuscle includes glomerular capillaries, podocytes, basement membrane Filtrate: fluid that passes across filtration membrane COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Nephron Components Nephron Components Proximal tubule: Distal tubule: where filtrate passes first structure between Loop of Henle and collecting duct Loop of Henle: Collecting duct: contains descending and ascending loops empties into calyces water and solutes pass through thin walls by diffusion carry fluid from cortex through medulla  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Flow of Filtrate through Nephron 1. Renal corpuscle 2. Proximal tubule 3. Descending loop of Henle 4. Ascending loop of Henle 5. Distal tubule 6. Collecting duct 7. Papillary duct COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Blood Flow Through the Kidney Blood Flow through Kidney 1. Renal artery 2. Interlobar artery 3. Arcuate artery 4. Interlobular artery 5. Afferent arteriole 6. Glomerulus 7. Efferent arteriole 8. Peritubular capillaries 9. Vasa recta 10. Interlobular vein 11. Arcuate vein 12. Interlobar vein  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Urine Formation Urine Formation Urine formation involves three processes: Filtration – occurs in the renal corpuscle Reabsorption – it involves removing substances from the filtrate and placing back into the blood Secretion – it involves taking substances from the blood at a nephron area other than the renal corpuscle and putting back into the nephron tubule Concentrations of Major Solutes in urine COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Urine Formation-Filtration Movement of water, ions, small molecules through filtration membrane into Bowman’s capsule 19% of plasma becomes filtrate 180 Liters of filtrate are produced by the nephrons each day 1% of filtrate (1.8 liters) become urine rest is reabsorbed  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Urine Formation-Filtration Only small molecules are able to pass through filtration membrane Formation of filtrate depends on filtration pressure Filtration pressure forces fluid across filtration membrane Filtration pressure is influenced by blood pressure Calculation of Renal Flow Rates COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Urine Production-Reabsorption 99% of filtrate is reabsorbed and reenters circulation Proximal tubule is primary site for reabsorption of solutes and water Descending Loop of Henle concentrates filtrate Reabsorption of water and solutes from distal tubule and collecting duct is controlled by hormones Reabsorption in the Proximal Convoluted Tubule Reabsorption of Major Solutes from the Nephron Reabsorption of Major Solutes from the Nephron  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Urine Concentration Urine Concentration The descending limb of the loop of Henle is a critical site for water The renal medulla contains very concentrated interstitial fluid that has reabsorption. large amounts of Na+, Cl−, and urea. The filtrate leaving the proximal convoluted tubule is further The wall of the thin segment of the descending limb is highly concentrated as it passes through the descending limb of the loop of permeable to water. Henle. As the filtrate moves through the medulla containing the highly The mechanism for this water reabsorption is osmosis. concentrated interstitial fluid, water is reabsorbed out of the nephron by osmosis. The water enters the vasa recta. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Urine Concentration The ascending limb of the loop of Henle dilutes the filtrate by removing solutes The thin segment of the ascending limb is not permeable to water, but it is permeable to solutes Consequently, solutes diffuse out of the nephron COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Reabsorption in the Loop of Henle Reabsorption in the Thick Segment of the Ascending Limb Distal Convoluted Tubule and Collecting Duct Reabsorption COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Urine Production—Secretion Tubular secretion removes some substances from the blood. These substances include by-products of metabolism that become toxic in high concentrations and drugs or other molecules not normally produced by the body. Tubular secretion occurs through either active or passive mechanisms.  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Secretion of Substances into the Nephron Urine Production—Secretion Ammonia secretion is passive. Secretion of H+, K+, creatinine, histamine, and penicillin is by active transport. These substances are actively transported into the nephron. The secretion of H+ plays an important role in regulating the body fluid pH. COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Urine Concentration and Volume Regulation Three major hormonal mechanisms are involved in regulating urine concentration and volume: 1. renin-angiotensin-aldosterone 2. the antidiuretic hormone (ADH) 3. the atrial natriuretic hormone  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Aldosterone Actions Renin-Angiotensin-Aldosterone Mechanism 1. Renin acts on angiotensinogen to produce angiotensin I 2. Angiotensin-converting enzyme converts angiotensin I to angiotensin II 3. Angiotensin II causes vasoconstriction 4. Angiotensin II acts on adrenal cortex to release aldosterone 5. Aldosterone increases rate of active transport of Na+ in distal tubules and collecting duct 6. Volume of water in urine decreases COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Antidiuretic Hormone Mechanism 1. ADH is secreted by the posterior pituitary gland 2. ADH acts of kidneys, causing them absorb more water (decrease urine volume) 3. Result is to maintain a normal blood volume and blood pressure  ADH and the Regulation of Extracellular Fluid COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Atrial Natriuretic Hormone 1. ANH is secreted from cardiac muscle in the right atrium of the heart when blood pressure increases 2. ANH acts on kidneys to decrease Na+ reabsorption 3. Sodium ions remain in nephron to become urine 4. Increased loss of sodium and water reduced blood volume and blood pressure  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Ureters and Urinary Bladder Ureters: small tubes that carry urine from renal pelvis of kidney to bladder Urinary bladder: in pelvic cavity stores urine can hold a few ml to a maximum of 1000 milliliters COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Ureters and Urinary Bladder Urethra Urethra: tube that exits bladder carries urine from urinary bladder to outside of body  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Micturition Reflex Urine Movement Micturition reflex: activated by stretch of urinary bladder wall action potentials are conducted from bladder to spinal cord through pelvic nerves parasympathetic action potentials cause bladder to contract stretching of bladder stimulates sensory neurons to inform brain person needs to urinate COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Body Fluid Compartments Composition of Fluids The intracellular fluid compartment includes the fluid inside all the Intracellular fluid contains a relatively high concentration of ions, such cells of the body. as K+, magnesium (Mg2+), phosphate (PO43−), and sulfate (SO42−), Approximately two-thirds of all the water in the body is in the compared to the extracellular fluid. intracellular fluid compartment. It has a lower concentration of Na+, Ca2+, Cl−, and HCO3− than does the The extracellular fluid compartment includes all the fluid outside the extracellular fluid. cells. The extracellular fluid compartment includes, interstitial fluid, plasma, lymph, and other special fluids, such as joint fluid, and cerebrospinal fluid. COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Composition of Fluids COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Exchange Between Fluid Compartments The cell membranes that separate the body fluid compartments are selectively permeable. Water continually passes through them, but ions dissolved in the water do not readily pass through the cell membrane. Water movement is regulated mainly by hydrostatic pressure differences and osmotic differences between the compartments. Osmosis controls the movement of water between the intracellular and extracellular spaces.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Regulation of Extracellular Fluid Composition Thirst Regulation Thirst Regulation Water intake is controlled by the thirst center located in the Ion Concentration Regulation hypothalamus When the concentration of ions in the blood increases, it stimulates the thirst center to cause thirst When water is consumed, the concentrations of blood ions decreases, due to a dilution effect; this causes the sensation of thirst to decrease COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Thirst Regulation of Extracellular Fluid Concentration COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Ion Concentration Regulation Regulating the concentrations of positively charged ions, such as Na+, K+, and Ca2+, in the body fluids is particularly important. Action potentials, muscle contraction, and normal cell membrane permeability depend on the maintenance of a narrow range of these concentrations. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Ion Concentration Regulation Sodium Ions Negatively charged ions, such as Cl−, are secondarily regulated by the Sodium ions (Na+) are the dominant ions in the extracellular fluid. mechanisms that control the positively charged ions. About 90 to 95% of the osmotic pressure of the extracellular fluid The negatively charged ions are attracted to the positively charged results from sodium ions and from the negative ions associated with ions; when the positively charged ions are transported, the negatively them. charged ions move with them. Stimuli that control aldosterone secretion influence the reabsorption of Na+ from nephrons of the kidneys and the total amount of Na+ in the body fluids. Sodium ions are also excreted in sweat.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Consequences of Abnormal Plasma Levels of Sodium Ions COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Potassium Ions Electrically excitable tissues, such as muscles and nerves, are highly sensitive to slight changes in the extracellular K+ concentration. The extracellular concentration of K+ must be maintained within a narrow range for these tissues to function normally. Aldosterone plays a major role in regulating the concentration of K+ in the extracellular fluid.  Regulation of Blood Potassium Levels Consequences of Abnormal Plasma Levels of Potassium Ions COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Consequences of Abnormal Concentrations of Calcium Ions Calcium Ions The extracellular concentration of Ca2+ is maintained within a narrow range. Increases and decreases in the extracellular concentration of Ca2+ have dramatic effects on the electrical properties of excitable tissues Parathyroid hormone (PTH), secreted by the parathyroid glands, increases extracellular Ca2+ concentrations. Calcitonin reduces the blood Ca2+ concentration when it is too high.  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Consequences of Abnormal Concentrations of Phosphate Ions Phosphate and Sulfate Ions Some ions, such as phosphate ions (PO43−) and sulfate ions (SO42−), are reabsorbed by active transport in the kidneys. The rate of reabsorption is slow, so that if the concentration of these ions in the filtrate exceeds the nephron’s ability to reabsorb them, the excess is excreted into the urine. As long as the concentration of these ions is low, nearly all of them are reabsorbed by active transport. COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Characteristics of Buffer Systems Regulation of Acid-Base Balance Buffers chemicals resist change in pH of a solution buffers in body contain salts of weak acids or bases that combine with H+ three classes of buffers: proteins, phosphate buffer, bicarbonate buffer  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Regulation of Acid-Base Balance Regulation of Acid-Base Balance Respiratory system involvement in acid-base: Kidney Involvement in acid-base: responds rapidly to changes in pH nephrons secrete H+ into urine and directly regulate pH of body fluids increased respiratory rate raises blood pH (more alkalotic) due to more H+ secretion if the pH is decreasing and less H+ secretion if pH is increased rate of carbon dioxide elimination from the body increasing reduced respiratory rate reduces pH (more acidic) due to decreased rate of carbon dioxide elimination from the body Regulation of Acid-Base Balance COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Acidosis and Alkalosis Acidosis occurs when the pH of blood falls below 7.35 There are two types of acidosis based upon the cause: respiratory and metabolic Alkalosis occurs when the pH of blood increases above 7.45 There are two types of alkalosis based upon the cause: respiratory and metabolic COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Clinical Impact  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Polycystic Kidney Disease Polycystic Kidney Disease Polycystic kidney disease is the third leading cause of renal failure In people affected by polycystic kidney disease, the kidneys are (after diabetes mellitus and high blood pressure). enlarged and often contain large, fluid-filled cysts varying in size from a few millimeters to centimeters. The cysts increase in number and Approximately 90% of patients inherit the condition as an autosomal enlarge as the person ages. dominant trait. Development of the cysts results from abnormal cell-to-cell interactions Consequently, if one parent carries an allele for this disorder, each child and causes excess proliferation of the epithelial cells that make up the has a 50% chance of also having the disorder. kidney nephrons and collecting ducts. The gene for this condition is located on chromosome 16 and codes for Polycystic kidney disease is often detected using ultrasound a protein that may regulate cell-to-cell interactions. techniques. The condition is usually diagnosed when patients are between 30 and 50 years of age. Approximately 50% of patients require hemodialysis by 70 years of age. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Diabetic Nephropathy and Renal Failure Diabetic Nephropathy and Renal Failure Diabetic nephropathy is a disease of the kidneys associated with The development of diabetic nephropathy is complex. Although the diabetes mellitus, and it is the principal cause of chronic renal failure. mechanism is not completely understood, the level of angiotensin II is elevated in diabetes mellitus. This condition damages renal glomeruli and ultimately destroys This causes exaggerated efferent arteriole vasoconstriction and functional nephrons through progressive scar tissue formation, consequently increased glomerular capillary pressure. mediated in part by an inflammatory response. The increased glomerular capillary pressure damages the glomerular basement membrane, causing it to thicken and become more The damaged glomeruli no longer filter the blood effectively, allowing permeable. proteins to pass through the filtration membrane and be excreted in The glomerular basement membrane is also damaged by the the urine. production of glycoproteins called advanced glycosylation end products The presence of protein in the urine of people who have type 2 (AGEs). diabetes strongly suggests significant diabetic nephropathy, which can lead to end-stage renal failure.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Diabetic Nephropathy and Renal Failure Diabetic Nephropathy and Renal Failure AGEs are produced when glucose forms irreversible cross-links with As the number of functional nephrons in the kidney decreases, kidney and plasma proteins. microalbuminuria eventually progresses to overt proteinuria, the The AGEs stimulate the secretion of growth factors from glomerular secretion of more than 300 mg albumin/day. cells, which promote glomerular basement membrane thickening. By the time overt proteinuria has developed, which may take 10–15 Because the glomerular basement membrane in patients with diabetes years, the number of functional nephrons has decreased to less than mellitus is more permeable than normal, plasma proteins cross the 10% of normal, and the kidneys are no longer able to excrete adequate filtration membrane and enter the urine. amounts of waste products. This condition is called end-stage renal disease (ESRD). The initial amount of protein entering the urine is small, a condition In ESRD, renal failure has worsened to the point that kidney function is called microalbuminuria. less than 10% of normal. Unless ESRD is treated by hemodialysis or kidney transplantation, the patient dies. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Diabetic Nephropathy and Renal Failure Diuretics The use of angiotensin-converting enzyme (ACE) inhibitors slows or, in some Diuretics are chemicals that increase the rate of urine production. cases, even halts the progression of proteinuria and end-stage renal disease. Diuretics are used to treat hypertension, as well as several types of ACE inhibitors prevent the formation of angiotensin II; consequently, arterial edema caused by congestive heart failure, cirrhosis of the liver, and blood pressure and glomerular capillary pressure remain within their normal other anomalies. ranges. Treatment with diuretics can lead to complications, including When ACE inhibitors are used in combination with drugs called angiotensin dehydration and electrolyte imbalances. receptor blockers (ARBs), which prevent angiotensin II molecules from binding to their receptors, proteinuria decreases up to 45%. People with type 2 diabetes who maintain their blood glucose within normal levels have a much lower incidence of diabetic nephropathy and ESRD.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Diuretics Diuretics The action of carbonic anhydrase inhibitors reduces the rate of H+ The diuretic effect is useful in treating conditions such as glaucoma and secretion and the reabsorption of bicarbonate ion (HCO3−). altitude sickness. As H+ is secreted into the renal tubule, it combines with HCO3− to form Long-term use, carbonic anhydrase inhibitors tend to lose their diuretic carbonic acid. effect. Carbonic acid dissociates into water and carbon dioxide, which can Sodium ion reabsorption inhibitors include thiazide-type diuretics. They diffuse across the wall of the renal tubule. promote the loss of Na+, Cl−, and water in the urine. Reduced H+ secretion causes HCO3− to remain in the renal tubule. The These diuretics are sometimes given to people who have hypertension. HCO3− increases tubular osmotic pressure, causing osmotic diuresis The increased loss of water in the urine lowers blood volume and thus blood pressure. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Diuretics Diuretics Other inhibitors of Na+ reabsorption, such as bumetanide, furosemide, Certain potassium-sparing diuretics act on the distal convoluted and ethacrynic acid, specifically inhibit transport in the ascending limb tubules and the collecting ducts to reduce the exchange between Na+ of the loop of Henle. and K+. These diuretics are frequently used to treat congestive heart failure, Potassium-sparing diuretics are used to diminish the loss of K+ in the cirrhosis of the liver, and renal disease. urine, thereby preserving, or “sparing,” these ions. A possible side effect of these drugs is increased excretion of K+ in the Some potassium-sparing diuretic drugs act by competitive inhibition of urine. aldosterone, whereas others inhibit the symporters for Na+ in apical membranes of cells in the distal convoluted tubules and collecting ducts.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Diuretics Diuretics Both types result in Na+ diuresis and K+ retention. A side effect of Osmotic diuretics freely pass into the filtrate and undergo limited prolonged treatment with certain diuretics is K+ depletion. reabsorption by the renal tubule. These diuretics are inhibitors of Na+–Cl− symporters in the ascending These diuretics increase urine volume by elevating the osmotic limb of the loop of Henle. concentration of the filtrate, thus reducing the amount of water To prevent K+ depletion, potassium-sparing diuretics are commonly moving by osmosis out of the renal tubule. used in combination with Na+–Cl− symport inhibitors. Urea, mannitol, and glycerine have been used as osmotic diuretics and can be effective in treating patients who have cerebral edema and edema in acute renal failure. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Diuretics Diabetes Insipidus Xanthines, including caffeine and related substances, act as diuretics The term Diabetes refers to a disease state characterized by polyuria, partly because they increase renal blood flow and the rate of excess production of urine. glomerular filtrate formation. There are two major causes of diabetes: They also influence the renal tubule by decreasing Na+ and Cl− 1) inadequate production of or response to insulin, called Diabetes reabsorption. Mellitus Alcohol acts as a diuretic, although it is not used clinically for that 2) inadequate production of or response to ADH, called Diabetes purpose. Insipidus. It inhibits ADH secretion from the posterior pituitary and results in increased urine volume.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Diabetes Insipidus Diabetes Insipidus Diabetes insipidus is a relatively rare disease that occurs in two NDI can also be acquired, but that usually happens later in life and can varieties: be due to several factors, including the use of certain prescription drugs Central diabetes insipidus (CDI) is caused by failure of ADH secretion, or the existence of an underlying systemic disease. and nephrogenic diabetes insipidus (NDI) results when ADH secretion Treatment of NDI includes ensuring a plentiful supply of water, is normal but the ADH receptor, or the response to ADH, in the kidney following a low-sodium and sometimes a low-protein diet, and using is abnormal. thiazide diuretics (Na+ reabsorption inhibitors) in combination with a Consequently, the G protein mechanism, which normally functions in potassium-sparing diuretic. the insertion of the aquaporin-2 water channel protein in the apical membranes, does not operate. In most cases, NDI results from an inherited condition that affects the function of the ADH receptor. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Kidney Stones Kidney Stones Kidney stones are hard objects usually found in the pelvis of the In addition to causing intense pain, kidney stones can block the ureter, kidney. cause ulceration in the ureter, and increase the probability of bacterial They are typically 2–3 mm in diameter, with either a smooth or a infection. jagged surface, but occasionally a large, branching kidney stone, called About 65% of all kidney stones are composed of calcium oxylate mixed a staghorn stone, forms in the renal pelvis. with calcium phosphate, whereas another 15% are magnesium About 1% of all autopsies reveal kidney stones, and many stones never ammonium phosphate and 10% are uric acid or cystine; approximately cause symptoms. The symptoms associated with kidney stones occur 2.5% of each kidney stone is composed of mucoprotein. when a stone passes into the ureter, resulting in referred pain down the The cause of kidney stones is usually obscure. back, side, and groin area. Predisposing conditions include concentrated urine and an abnormally The ureter contracts around the stone, causing the stone to irritate the high calcium concentration in the urine, although the cause of the high epithelium and produce bleeding, which appears as blood in the urine, calcium concentration is usually unknown. a condition called hematuria.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Kidney Stones Acidosis and Alkalosis Magnesium ammonium phosphate stones are often found in people The normal pH of the body fluids is between 7.35 and 7.45. with recurrent kidney infections, and uric acid stones are common in When the pH is below 7.35, the condition is called acidosis; when the people suffering from gout. pH is above 7.45, it is called alkalosis. Severe kidney stones must be surgically removed from the kidney. Metabolism produces acidic products that lower the pH of the body However, traditional surgical procedures have mainly been replaced by fluids. For example, CO2 is a by-product of metabolism that combines lithotripsy, in which kidney stones are pulverized using ultrasound or with water to form H2CO3. lasers. Likewise, anaerobic respiration produces lactic acid, protein metabolism produces phosphoric and sulfuric acids, and lipid metabolism produces fatty acids. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Acidosis and Alkalosis Acidosis and Alkalosis These acidic substances must continuously be eliminated from the The major effect of acidosis is depression of the central nervous body to maintain homeostatic pH. system. When blood pH falls below 7.35, the central nervous system Failure to eliminate the acidic products of metabolism results in malfunctions. The individual becomes disoriented, and possibly acidosis. comatose as the condition worsens. Excess elimination of the acidic products of metabolism results in A major effect of alkalosis is hyperexcitability of the nervous system. alkalosis. Peripheral nerves are affected first, resulting in spontaneous nervous stimulation of muscles. Spasms, tetanic contractions, and possibly extreme nervousness or convulsions result. Severe alkalosis can cause death as a result of tetany of the respiratory muscles.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Acidosis and Alkalosis Acidosis and Alkalosis Although buffers help resist changes in the pH of body fluids, the Inadequate ventilation of the lungs causes respiratory acidosis. respiratory system and the kidneys regulate the pH of the body fluids. The rate at which CO2 is eliminated from the body fluids through the Therefore, malfunctions in either the respiratory system or the kidneys lungs falls. can result in acidosis or alkalosis. This increases the concentration of CO2 in the body fluids. As CO2 levels Acidosis and alkalosis are categorized according to the cause of the increase, CO2 reacts with water to form H2CO3. condition. Carbonic acid forms H+ and HCO3−. The increase in H+ concentration Respiratory acidosis and alkalosis result from abnormalities in the causes the pH of the body fluids to decrease. respiratory system. If the pH falls below 7.35, the symptoms of respiratory acidosis appear. Metabolic acidosis and alkalosis result from all causes other than abnormal respiratory functions. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Acidosis and Alkalosis Acidosis and Alkalosis Buffers help resist a decrease in pH, and the kidneys help compensate For example, the kidneys cannot compensate for respiratory acidosis for the failure of the lungs to prevent respiratory acidosis by increasing occurring in response to a severe asthma attack that begins quickly and the rate at which they secrete H+ into the filtrate and reabsorb HCO3−. subsides within hours. If, however, respiratory acidosis results from emphysema, which develops over a long time, the kidneys play a significant However, the capacity of buffers to resist changes in pH can be role in helping compensate. exceeded, and a period of 1–2 days is required for the kidneys to become maximally functional. Respiratory alkalosis results from hyperventilation of the lungs. This increases the rate at which CO2 is eliminated from the body fluids and results Thus, the kidneys are not effective if respiratory acidosis develops in a decreased concentration of CO2 in the body fluids. As CO2 levels quickly. On the other hand, the kidneys are very effective if respiratory decrease, H+ reacts with HCO3− to form H2CO3. acidosis develops slowly, or if it lasts long enough for the kidneys to The resulting decrease in the concentration of H+ causes the pH of the body respond. fluids to increase. If the pH increases above 7.45, the symptoms of respiratory alkalosis appear.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Acidosis and Alkalosis Acidosis and Alkalosis The kidneys help compensate for respiratory alkalosis by decreasing the Metabolic acidosis results from all conditions that decrease the pH of rate of H+ secretion into the filtrate and the rate of HCO3− the body fluids below 7.35, with the exception of those resulting from reabsorption. altered function of the respiratory system. If pH increases, the kidneys need 1–2 days to compensate. Thus, the As H+ accumulates in the body fluids, buffers first resist a decline in pH. kidneys are not effective if respiratory alkalosis develops quickly. If the buffers cannot compensate for the increase in H+, the respiratory However, they are very effective if respiratory alkalosis develops slowly. center helps regulate body fluid pH. For example, the kidneys are not effective in compensating for The reduced pH stimulates the respiratory center, which causes respiratory alkalosis that occurs in response to hyperventilation hyperventilation. During hyperventilation, CO2 is eliminated at a triggered by emotions, which usually begins quickly and subsides greater rate. within minutes or hours. The elimination of CO2 also eliminates excess H+ and helps maintain the However, if alkalosis results from staying at a high altitude over a 2- or pH of the body fluids within a normal range. 3-day period, the kidneys play a significant role in helping compensate. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Acidosis and Alkalosis Acidosis and Alkalosis If metabolic acidosis persists for many hours and if the kidneys are Metabolic alkalosis results from all conditions that increase the pH of functional, the kidneys can also help compensate for metabolic acidosis the body fluids above 7.45, with the exception of those resulting from by secreting H+ at a greater rate and increasing the rate of HCO3− altered function of the respiratory system. reabsorption. As H+ decreases in the body fluids, buffers first resist an increase in pH. The symptoms of metabolic acidosis appear if the respiratory and renal If the buffers cannot compensate for the decrease in H+, the systems are not able to maintain the pH of the body fluids within its respiratory center helps regulate body fluid pH. normal range. The increased pH inhibits respiration. Reduced respiration allows CO2 to accumulate in the body fluids. Carbon dioxide reacts with water to produce H2CO3. If metabolic alkalosis persists for several hours and if the kidneys are functional, the kidneys reduce the rate of H+ secretion to help reverse alkalosis.  Acidosis and Alkalosis COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Systems Pathology COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Acute Renal Failure Acute Renal Failure Acute renal failure can be caused by prolonged low blood pressure and Blood levels of urea and creatine usually increase due to reduced lack of blood flow to the kidneys. filtrate formation and reduced function of the tubular epithelium. If the reduced blood flow is severe enough it can cause damage to the A small amount of urine is produced that has a high Na+ concentration, epithelial lining of the kidney tubules. although the osmolality is usually close to the concentration of the And a period of reduced urine volume can be experience resulted from body fluids. tubular damage. Dead and damaged tubular cells sloughed off into the The kidney is not able to reabsorb Na+, nor can it effectively tubules and blocked them, so that filtrate could not flow through. concentrate urine. In addition, the filtrate leaked from the blocked or partially blocked tubules back into the interstitial spaces and therefore back into the circulatory system. As a result, the amount of filtrate that became urine was markedly reduced.  COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Treatments for Renal Failure Treatments for Renal Failure Hemodialysis is used when a person is suffering from severe acute or On the outside of the dialysis tubes is a fluid, called dialysis fluid, which chronic kidney failure. contains the same concentration of solutes as normal plasma, except The procedure substitutes for the excretory functions of the kidney. for the metabolic waste products. As a consequence, the metabolic wastes diffuse from the blood to the dialysis fluid. Hemodialysis is based on blood flow through tubes composed of a selectively permeable membrane. The dialysis membrane has pores that are too small to allow plasma proteins to pass through them, and because the dialyis fluid contains Blood is usually taken from an artery, passed through tubes of the the same beneficial solutes as the plasma, the net movement of these dialysis machine, and then returned to a vein. substances is zero. COLLEGE OF MEDICAL TECHNOLOGY COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Calayan Educational Foundation, Inc. Treatments for Renal Failure Treatments for Renal Failure Peritoneal dialysis is sometimes used to treat kidney failure. Kidney transplants are sometimes performed on people who have The principles by which peritoneal dialysis works are the same as for severe renal failure. hemodialysis, but the dialysis fluid flows through a tube inserted into Often, the donor has suffered an accidental death and had granted the peritoneal cavity. permission to have his or her kidneys used for transplantation. The visceral and parietal peritonea act as the dialysis membrane. The major cause of kidney transplant failure is rejection by the Waste products diffuse from the blood vessels beneath the recipient’s immune system. peritoneum, across the peritoneum, and into the dialysis fluid  COLLEGE OF MEDICAL TECHNOLOGY Calayan Educational Foundation, Inc. Hemodialysis Treatments for Renal Failure Physicians therefore attempt to match the immune charcteristics of the donor and recipient to reduce the tendency for rejection. Even with careful matching, recipients have to take medication for the rest of their lives to suppress their immune reactions. In most cases, the transplanted kidney functions well, and the tendency of the recipient’s immune system to reject the transplanted kidney can be controlled. Acute Renal Failure Representative Diseases and Disorders: Urinary System